The ability to determine rotations of an object is useful for numerous different applications. For example, fleet maintenance agreements, leasing agreements and/or certain governmental regulations often require the use of a device to accurately record the distance traveled by a commercial vehicle. One device, commonly known as a hubodometer, is typically bolted or otherwise attached to a wheel hub of the vehicle where it senses rotation of the wheel, the sensed rotation being correlated with distance traveled. Such distance information may be used, for example, for determining highway usage fees as well as for compliance with contractual agreements. Given the potentially costly outcome of inaccurate measurements, it is important that the recording device be manufactured in a manner which prevents intentional or inadvertent alteration of the distance information. It is also important that the recording device not be sensitive to transient movements or vibrations of the device such that such movements are not interpreted as a rotation of the wheel hub.
Traditional solutions to this problem have included using a weighted mechanical assembly that sits along the rotating axis of a wheel. As the wheel turns, the weighted assembly stays stationary. This provides a relative motion that can drive a geared odometer. The problems with this method are that vibration can induce spin into the weighted assembly which makes the unit stop counting since there is no longer any relative motion with respect to the wheel to turn the internal gears. This forces the unit to inherently undercount over time. Another limitation to this method is that every wheel needs different parts and gears so that mileage is displayed correctly on different wheel sizes. Not all wheel sizes can be supported in this manner though. A further limitation relates to the effect of wheel impacts when driving over rough surfaces or rocks. These impacts can impart inaccuracies into the odometer count.
Prior electronic hubodometers are known, such as described in U.S. Pat. No. 6,940,940, entitled “Electronic Hubodometer” and issued on Sep. 6, 2005, the entire disclosure of which is incorporated herein by reference. In this disclosure, a hubodometer is provided with a single accelerometer that is operable to sense a force acting thereon and generate an electrical signal representative of said force. Further an electronic control system is provided comprising a microcontroller and power source, the microcontroller comprising electronic filtering means for attenuating irregularities in the signal from the sensor means and computing a wheel revolution count based on said attenuated signal, and output means for communicating the wheel revolution count. The accelerometer preferably comprises a dual axis electronic accelerometer with no internally rotating parts. Further, the output means preferably comprises at least one of a display means, an IR communication system, and/or a RF communications system.